Conservation of Mechanical Energy Requires Mass

Steps:

• Initial potential energy is mgh, where h = 12 m and g ≈ 9.8 m/s².
• Stone dropped from rest, so initial kinetic energy = 0 J.
• Air resistance negligible, so total mechanical energy conserved.
• Just before ground, potential energy = 0 J, so kinetic energy = mgh.

Not enough information: Mass m of stone not given, so numerical kinetic energy cannot be calculated.

Why A is correct: Not applicable; no option correct due to missing mass.

Why the others are wrong:

• B, C, D: All incorrect for same reason—insufficient data to determine exact value.

Final answer: Not enough information.